In general, there is formed a circuit wiring on a substrate such as a semiconductor wafer or a liquid crystal substrate for forming a semiconductor device. As a method of forming a wiring, there has been used a damascene method in which a recess such as a via or a trench for burying a wiring material such as copper is formed in the substrate and the wiring material is buried in the recess.
Further, in recent years, there has been made an attempt to reduce a mounting area of a part or a whole system by mounting multiple LSIs on a substrate using a three-dimensional mounting technology. In the three-dimensional mounting technology, a recess, e.g., a through-silicon-via (TSV), for burying a wiring material, which connects the LSIs, is formed, for example, in a substrate (e.g., a silicon substrate).
Between an inner surface of a recess in a substrate and a wiring formed in the recess, typically, there is formed a barrier film for suppressing diffusion of atoms constituting a wiring material into an insulating film (an oxide film, PI “polyimide”, etc.) on the inner surface of the recess and into the substrate on a rear surface side thereof, or for improving adhesivity therebetween. Further, between the barrier film and the wiring, typically, there is formed a seed film for making it easy to bury the wiring material.
By way of example, in Patent Document 1, there is suggested a method in which a barrier film containing ruthenium is formed on an inner surface of a recess by sputtering, a seed film containing ruthenium and copper is formed on the barrier film by sputtering, and then, copper is buried in the recess by a plating process.
Patent Document 1: Japanese Patent Laid-open Publication No. 2010-177538
In recent years, there has been developed a manufacturing technique employing a TSV. In this manufacturing technique, a height or a depth of a recess in the TSV is not in a range of several tens of nanometers to several hundreds of nanometers in a conventional pre-treatment process but in a range of several microns to several hundreds of microns.
By way of example, a sputtering method which has been typically used for forming a barrier film or a seed film has a high directionality. For this reason, if a recess has a great height or depth, it is difficult to sufficiently form a barrier film or a seed film on a lower portion of the recess.
In order to solve such problems, a plating method such as an electroplating process or an electroless plating process, in which a plating liquid is supplied while rotating a substrate, may be considered. However, if a recess has a small diameter and a great height or depth, a plating liquid within the recess has a low fluidity, which may cause non-uniformity in concentration distribution of the plating liquid between an upper portion of the recess and a lower portion thereof. If there is non-uniformity in the concentration distribution of the plating liquid within the recess, it can be assumed that a thickness of a plating layer such as a barrier film or a seed film formed on an inner surface of the recess varies depending on positions within the recess. By way of example, it can be assumed that a thickness of a plating layer formed on the lower portion of the recess may be smaller than that of a plating layer formed on the upper portion of the recess.
For this reason, there has been developed a method in which a first plating layer is formed by supplying a first plating liquid onto a substrate and then a second plating layer is formed on the first plating layer by supplying a second plating liquid onto the substrate. In this case, the first plating layer is mainly formed on a surface of the substrate and the second plating layer is formed on an inner surface of a recess. However, even if there is used the method of forming the first plating layer and the second plating layer in sequence, it is difficult to uniformly form the first plating layer on the entire surface of the substrate and also uniformly form the second plating layer on the inner surface of the recess.
The exemplary embodiments have been accomplished in view of the foregoing problems. According to the exemplary embodiments, it is possible to uniformly form a first plating layer on an entire surface of a substrate and also uniformly form a second plating layer on an inner surface of a recess, and it is possible to uniformly form a plating layer formed on inner surfaces of recesses on the entire surface of the substrate. Further, the exemplary embodiments provide a plating method and a plating apparatus of improving uniformity in thickness of the plating layer formed on the inner surfaces of the recesses on the entire surface of the substrate, and a storage medium therefor.